(1) Field of Invention
Shading and heat insulating structures.
(2) Description of Prior Art
Shades which, by reflecting and cutting off, and in some instances absorbing, the direct rays radiating from the sun while transmitting the indirect rays reflected from objects in the sunlight, discriminate between direct radiation and diffused indirect radiation emanating from the source, are known in the art. Such are disclosed in U.S. Pat. No. 3,443,860, issued May 13, 1969, entitled "Pleated Sheet for Controlling Heat and Light", and U.S. Pat. No. 3,684,352, issued Aug. 15, 1972, and entitled "Radio-Chromic Combined Absorbing, Reflecting and Transmitting Structure."
As disclosed in the earlier of the above patents, the shade comprises a sheet of transparent light transmitting material having a light reflecting coating on the portions of one side of each pleat providing show areas. These areas are so arranged that when the pleats are in open formation, the show areas intercept direct sun rays and prevent them from reaching so-called shade areas of the pleats. Usually the shade area of each pleat is the other side of the pleat, plus an adjacent portion of each pleat between said other side and the coated show area thereof. With this structure, the rays of the high sun are intercepted by the show areas and reflected back toward the source. The shade areas are shaded by these show areas but permit the passage of indirect light therethrough into the room and also afford a view of the outside by a person in a room. However, at low levels of the sun, it often happens that the direct rays, approaching horizontal, pass through the clear shade portions of the sides of the pleats adjacent the show areas.
At first this disadvantage was overcome by coating the entire face of one side of each pleat with the opaque reflecting material, but this resulted in a sacrifice of indirect light and a decrease in the vision of the outside. Next, as described in the above U.S. Pat. No. 3,684,352, this disadvantage was sought to be overcome by making the shade of a sheet of radio-chromic material, pleated in like fashion, but without any coating. With the latter shade the show areas expand and contract, depending upon which areas are struck by the direct sun rays. Those struck darken and provide the show areas which shade other areas, leaving the other or shade areas clear for viewing the outside and for permitting the passage of indirect and less intense light therethrough. However, it often happens that the radio-chromic material is not as highly reflective as desired when dark and is very expensive.